The Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards provide a set of wireless local area network (WLAN) standards for relatively short-range communications ranging from tens of meters to a few hundred meters. With the IEEE 802.11 standard, data rates as high as 300 Mbps (megabits per second) are achievable over a defined frequency range. The 802.11ac standard, currently under development, aims to triple that data rate.
The history of IEEE 802 wireless standards begins with the IEEE 802.11a/b/g standards implemented from 1997 to 2003. In 2009, the IEEE 802.11n standard introduced substantial enhancements to WLAN performance, efficiency and robustness of the IEEE 802.11 physical (PHY) and medium access control (MAC) layers. In particular, 802.11n introduced a new multi-streaming modulation technique. As such, products designed in compliance with the IEEE 802.11n standard achieved by as much as five times the throughput and up to double the range over legacy IEEE 802.11 a/b/g technologies.
The currently proposed IEEE 802.11ac standard provides further improvements to the IEEE 802.11n standard. The IEEE 802.11ac standard will continue to work in the five gigahertz (GHz) band, but will provide larger channels for data throughput. Devices based on IEEE 802.11ac will be using channels that are either 40 megahertz (MHz) or 80 MHz wide, and perhaps even 160 MHz wide, to deliver data. Devices based on IEEE 802.11ac may also make use of multiple user, multiple inputs, multiple outputs (MU-MIMO) to transmit simultaneous data streams to different users on the same channels.
In the IEEE 802.11n standard, a low density parity-check (LDPC) code has been adopted for use as an error correcting code. LDPC is a class of linear block codes, and provides for linear error correcting. As such, LDPC provides a method for transmitting messages over noisy transmission channels without losing information. LDPC codes can be decoded in time linear to their block length. As such, LDPC encoding in compliance with IEEE 802.11n by the transmitting device allows the receiving device to derive all LDPC parameters in a packet.
In the proposed IEEE 802.11ac standard, the conventional LDPC encoding process may be changed. The proposed changes can create problems for LDPC decoding on the receive side. For instance, the receiving device may not recognize some signaling components (e.g., LDPC coding parameters) that result from the aforementioned changes. In addition, even if the receiving device recognizes these new signaling components, mapping issues may remain between LDPC components.